RETROGRESSION. 



103 



Evidently the snake did not come from 

 the lizard by accumulation of beneficial 

 differences, and common-sense will not enter- 

 tain the idea that the limbs and even their 

 bones wholly disappeared by disuse, or that 

 the additional vertebrae came by excessive 

 use, or that these transformations were 

 brought about by changes in conditions of 

 existence. 



An antecessor of the whale was a four- 

 legged land animal a mammal, and the 

 whale remains a mammal ; but its fore- 

 limbs have become converted into fins, and 

 the hind are replaced by a huge tail. The 

 whale is thus well adapted for a life in 

 the sea instead of on land, but his organs f 

 of locomotion are less highly specialised than 

 those of the four-legged antecessor. 



Is it possible to conceive that transforma- 

 tions so great one pair of legs into fins 

 and the other pair into a tail could have 

 been brought about by natural selection, 

 accumulation of beneficial differences, use or 

 disuse, or changed conditions of existence ? 



How, then, does Darwin's theory explain 

 these changes? 



So far as we can find, neither he nor 

 Huxley attempts any explanation, or indeed 

 refers to the very remarkable retrogression in 



